General Circulation Diagnosis in the Pressure-Isentrope Hybrid Vertical Coordinate

Iwasaki, Toshiki

doi:10.2151/jmsj1965.70.2_673

Cited by 36 publications

(31 citation statements)

References 41 publications

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“…The analysis of MMC and eddy mixing is based on massweighted isentropic zonal means (hereafter referred to as MIM analysis; Iwasaki, 1989Iwasaki, , 1992Miyazaki and Iwasaki, 2005). The MIM zonal mean is defined as…”

Section: Analysis Frameworkmentioning

confidence: 99%

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Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis data sets

et al. 2016

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Abstract. The stratospheric mean-meridional circulation (MMC) and eddy mixing are compared among six meteorological reanalysis data sets: NCEP-NCAR, NCEP-CFSR, ERA-40, ERA-Interim, JRA-25, and JRA-55 for the period 1979-2012. The reanalysis data sets produced using advanced systems (i.e., NCEP-CFSR, ERA-Interim, and JRA-55) generally reveal a weaker MMC in the Northern Hemisphere (NH) compared with those produced using older systems (i.e., NCEP/NCAR, ERA-40, and JRA-25). The mean mixing strength differs largely among the data products. In the NH lower stratosphere, the contribution of planetaryscale mixing is larger in the new data sets than in the old data sets, whereas that of small-scale mixing is weaker in the new data sets. Conventional data assimilation techniques introduce analysis increments without maintaining physical balance, which may have caused an overly strong MMC and spurious small-scale eddies in the old data sets. At the NH mid-latitudes, only ERA-Interim reveals a weakening MMC trend in the deep branch of the Brewer-Dobson circulation (BDC). The relative importance of the eddy mixing compared with the mean-meridional transport in the subtropical lower stratosphere shows increasing trends in ERA-Interim and JRA-55; this together with the weakened MMC in the deep branch may imply an increasing age-of-air (AoA) in the NH middle stratosphere in ERA-Interim. Overall, discrepancies between the different variables and trends therein as derived from the different reanalyses are still relatively large, suggesting that more investments in these products are needed in order to obtain a consolidated picture of observed changes in the BDC and the mechanisms that drive them.

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Section: Analysis Frameworkmentioning

confidence: 99%

“…The MIM analysis thus expresses the conservative nature of momentum, heat, and minor constituents, including the exact lower boundary conditions and non-geostrophic effects (Iwasaki, 1989(Iwasaki, , 1992. The MIM analysis also exactly specifies the eddy diabatic and adiabatic transport terms (Miyazaki and Iwasaki, 2005).…”

Section: Analysis Frameworkmentioning

confidence: 99%

Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis data sets

et al. 2016

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“…In MIM, zonal mean zonal momentum equation based on isentropic zonal mean pressure p † is written in a spherical form (Iwasaki 1992;Tanaka et al 2004) as…”

Section: Appendixmentioning

confidence: 99%

“…In MIM, very differently from the conventional zonal mean, the mass stream function has a distinct extratropical tropospheric direct (ETD) circulation in the winter hemispheres, in addition to the Hadley circulation (Iwasaki 1989 and1992;Juckes et al 1994;Juckes 2001). In particular, the strong zonal mean equatorward flow appears in the lower troposphere.…”

Section: Introductionmentioning

confidence: 98%

“…The mass-weighted isentropic zonal mean (MIM) enables us to describe the Lagrangian mean meridional circulation (Gallimore et al 1981;Andrews 1983;Townsend et al 1985;Tung 1986;Iwasaki 1989Iwasaki , 1990Iwasaki and 1992Juckes et al 1994;Juckes 2001). In MIM, very differently from the conventional zonal mean, the mass stream function has a distinct extratropical tropospheric direct (ETD) circulation in the winter hemispheres, in addition to the Hadley circulation (Iwasaki 1989 and1992;Juckes et al 1994;Juckes 2001).…”

Section: Introductionmentioning

confidence: 99%

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Mass-Weighted Isentropic Zonal Mean Equatorward Flow in the Northern Hemispheric Winter

Iwasaki

Mochizuki

2012

SOLA

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In the diagnosis of mass-weighted isentropic zonal mean (MIM), the mean-meridional circulation has a strong extratropical direct (ETD) cell in the northern-hemispheric winter, which turns from downward to equatorward around 45°N and isentropic zonal mean pressure of 850 hPa. The January mean equatorward flow in the extratopical lower troposphere is almost in balance with Eliassen-Palm (E-P) flux divergence for both climatology and interannual variability. This means that the zonal mean equatorward flow in the extratropical lower troposphere is the wave-induced circulation as well as the poleward flow in the stratosphere is.The interannual variation of January mean mass stream functions at (45°N, 850 hPa) positively (negatively) correlates with the zonal mean temperature in the lower troposphere north (south) of about 45°N, respectively. This is consistent with a simple thermodynamic consideration that the strong ETD circulation adiabatically warms up the lower troposphere due to the descending flow in the higher latitudes but cools it down due to the heat advection by the equatorward flow in the middle latitudes (~35°N).

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Brewer‐Dobson circulation diagnosed from JRA‐55

Kobayashi¹,

Iwasaki

2016

JGR Atmospheres

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We examine the Brewer-Dobson circulation (BDC) in the lower stratosphere diagnosed from the Japanese 55 year Reanalysis (JRA-55) data set and compare it with the BDCs diagnosed from the other reanalyses (i.e., ERA-Interim and JRA-25), and JRA-55-related data sets (i.e., JRA-55C, created by assimilating only in situ observations, and JRA-55AMIP, a simulation by a prediction model). The climatological mean seasonal change of the BDC in JRA-55 is similar to that in ERA-Interim but considerably different from that in JRA-25. Dynamical and thermodynamical consistencies among the variables are greatly improved in the JRA-55 data set. The interannual variations of the annual mean tropical upwellings in JRA-55 are almost coincident with those in JRA-55C. It suggests that the weakly increasing trend of the BDC found in JRA-55 does not have anything to do with changes in the satellite observing system. The climatological mean tropical upwelling diagnosed from JRA-55 is stronger than that from JRA-55AMIP. This difference is presumed to partly link to the model's inability to simulate the quasi-biennial oscillation (QBO). The JRA-55AMIP data set, a simple simulation performed without data assimilation, does not simulate the QBO, whereas the JRA-55 data set represents the QBO with the aid of data assimilation. The climatological mean zonal mean states of JRA-55AMIP considerably deviate from those of JRA-55 in the lower stratosphere. The deviation of JRA-55AMIP is similar to the modulation pattern by the QBO in specific phase regions in which the BDC is rather weak. The simulated QBO might enhance the BDC and reduce the model biases in the tropical lower stratosphere.

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General Circulation Diagnosis in the Pressure-Isentrope Hybrid Vertical Coordinate

Cited by 36 publications

References 41 publications

Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis data sets

Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis data sets

Mass-Weighted Isentropic Zonal Mean Equatorward Flow in the Northern Hemispheric Winter

Brewer‐Dobson circulation diagnosed from JRA‐55

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